Electronic animal control systems are known in which a radio frequency receiver collar is attached to an animal to limit the movement of the animal within a predetermined area of confinement. Traditionally, the predetermined area is configured through the physical arrangement of a subterranean transmission antenna which transmits a unique electromagnetic signal produced by an operably linked transmitting device. The transmission pattern of the subterranean antenna creates zones of transmission, or area "boundaries," in which the attached animal receiver collar is responsive to the uniquely transmitted electromagnetic signal. Upon entering a predetermined limit area, the receiver collar is adapted to detect the unique electromagnetic signal and, in response, deliver a correction stimulus, such as a mild shock or audible signal, to the animal. The effect of the repeated stimulus teaches the animal, such as a dog, to avoid the limit areas thus confining the animal without use of physical fences or barriers.
Alternatively, variations of this technology are known to keep animals out of small predefined areas such as outdoor patios and decks, as well as indoor rooms such as nurseries and home offices. In these applications a radio frequency transmission station is located in a room or area in which animals are to be excluded. The omnidirectional transmission of the RF signal creates a spherical zone of transmission or "exclusion area" in which the attached animal's radio frequency receiver collar is responsive to the uniquely transmitted electromagnetic signal. Upon entering the predetermined area, the receiver collar is adapted to detect the unique electromagnetic signal and, in response, deliver a correction stimulus to the animal.
Presently, design limitations inherent to such radio frequency systems has affected their reliability and effectiveness. One limitation of these pet containment/barrier systems is the incidental conductive structures present in most containment/barrier environments. These structures can couple and re-radiate the radio frequency signal into undesired areas. The incidental structures function as "coupling structures" relative to the RF transmitter signal radiated from the transmission station antenna. For example, residential locations are supplied with various utilities, such as water, cable television, electrical power, telephone service, and the like, by overhead or subterranean conductors (conduit, pipes, wires, cables, etc.) that cross property lines of the residence and then are distributed throughout the residence. Depending upon the topology of the conductors or their proximity to the transmitting antenna along their respective routes, the transmitter signal can induce a similar signal within such conductors. The conductors may then, in effect, distribute the transmitter signal to undesired locations at the residence by re-radiating the induced signal along their respective routes.
The primary undesirable result of the presence of incidental coupling structures is that the animal occasionally receives the correction stimulus in areas where the stimulus is not intended to be applied. The constant presence of the RF stimulus enable signal further contributes to the probability that the collar stimulus will occasionally be delivered accidentally. Such unintended stimulation of a dog can habituate the dog to being stimulated by the receiver, thus contributing to the decreased effectiveness of the RF electronic animal control system to control the dog. Additionally, such unintended simulation can contribute to undesirable behavior of the dog.
A further limitation of RF based systems is the inability these systems to precisely direct or configure the detection zone created by the RF transmission pattern. The RF signal is omnidirectionally radiated, creating a spherical transmission pattern emanating from the point of origin, or transmission antenna. Thus, systems are unable to focus their transmissions in the direction of an animals likely approach such as a doorway. Moreover, depending on the orientation of the collar, the collar may detect transmission levels of varying intensity. For example, when an animal raises and lowers its head the collar travels through the spherically radiated magnetic flux lines of the RF antenna, causing the animals collar to detect an RF signal of varying intensity.
The system in accordance with the present invention is provided for the exclusion/containment of animals to a predefined area. A directional ultrasonic transmission station defining a transmission reference point, selectively transmits a stimulus transmission in response to an ultrasonic animal collar transponder signal calculated to be in the predefined range of the transmission reference point by the transmission station.